When no systemd profile is used, or there is no systemd profile available for the system architecture, add the following code
to /etc/portage/profile/packages so that sys-apps/openrc is not pulled in as a system dependency since OpenRC and systemd conflict.

Code:

FILE /etc/portage/profile/packages

# Remove OpenRC from the system profile when using systemd
-*sys-apps/openrc

The remainder of the Gentoo Handbook focuses on OpenRC as the default init support system. If systemd is wanted instead, or you are planning to use Gnome 3.8 and later (which requires systemd), please consult the systemd page as it elaborates on the different configuration settings and methods.